In manufacturing process of semiconductor devices such as PN diodes or IGBTs, irradiation with an electron beam or various particle beams such as a proton beam and a helium ion beam can be performed in order to control their carrier lifetime. For example, Patent Document 1 discloses a PN diode in which crystal defects are formed near the interface of the PN junction by implanting protons. Irradiation to silicon crystals with a particle beam introduces crystal defects, and decreases the carrier lifetime accordingly. A desirable lifetime can be obtained by controlling the irradiation quantity.
The following is a process to form a defect in a silicon single crystal with particle beam irradiation. First, when particle beams are implanted, silicon atoms composing a crystal is sprung out from the lattice position to form interstitial silicons (I) and monovacancies (V). This pair of the interstitial silicon and the monovacancy is referred to as a Frenkel pair.
A part of the interstitial silicons is replaced to a carbon atom Cs existing at the lattice position to form an interstitial carbon Ci. This interstitial carbon is unstable, and accordingly bonds to an interstitial oxygen or other substitutional carbon to form a composite defect such as CiOi or CiCs respectively. It is considered that the rest of the interstitial silicons will form clusters by agglomerating with other interstitial silicons, remain intact in the crystals, or bond with monovacancies again to disappear.
It is known that the defects due to interstitial carbons such as CiOi and CiCs can be detected by photoluminescence (PL) or cathode luminescence (CL) and are influenced by oxygen concentration or carbon concentration in the crystal (Non-Patent Document 1).
On the other hand, it is considered that the monovacancy in the Frenkel pair comes to be stable state when the monovacancy locates in a particular position with another monovacancy, and many of them form VV defects composed of two silicon atom vacancies. There is an example to evaluate this defect by electron spin resonance (ESR) analysis (Non-Patent Document 2).